OK, where were we?
Oh yes, I reckon I should give @
DarkPira7e , a straight answer.
When I was a kid, I was taught to address adults as, Mr., Mrs., Doctor, or Uncle/Aunt, Grandpa/Grandma, Mom/Dad, as the case my be.
When I was in college, I addressed instructors as Professor (last name).
When I was in the Army, I addressed all fellow soldiers as to their rank, followed by their last name. Even when I was intoxicated in the Officers Club, I still addressed junior officers by their rank and last name. Why? Because it's tough to send a soldier on a risky mission if you are on a first name basis with them. As far as other officers of equal rank, I would address them by their first name, if I liked them, and by their rank followed by their last name, if I didn't.
Back in civilian life, working in a research environment, I would address other professional people that I met as Dr. (last name), until they corrected me or told me to just call them by their first name.
In the corporate HQ world (Stauffer Chemical Company), I would usually address people by their first names. Why? Because by the time people got to that level, "titles" didn't mean shit. Positioning and salary was all that mattered.
When I was working in a higher education/research environment (IITRI) (Illinois Institute of Technology Research Institute), I addressed the people I met as Dr. (last name) which was correct 90% of the time. Most of them expected that.
When I was working for a Biotechnology start up company (TSI) (Transgenic Sciences Inc.) everybody called everybody else by their first name, as they scurried around in their jeans and sweatshirts, placing and adjusting mirrors, forming smoke and preparing for an IPO.
As a real estate broker (Coldwell Banker), I addressed people by their first names, unless they were a medical doctor client. If anyone tried to "pull rank" on me, I would tell them to f**k off and go find another broker.
In my retirement years, I am known as Dad, Pa-pa or (whatever mrs humfrz decides to call me, depending on the situation.) I usually address people as sir or hon, because I usually can't remember either their first or last name.
humfrz